Antenna



p 1949- I D. w. MARTIN 2,483,217

ANTENNA Filed April 21, 1947 I I I I4 l j 5 g I? l l9 I2 27 25 5'1 20 I5 a I6 :II :I i 2 ll I H I :1 2| I l E I0 I 2 DAVID W. MARTIN I mm Patented Sept. 2?, 1949 ANTENNA David W. Martin, Baltimore, Md., assignor to Bendix Aviation Corporation, Towson, Md, a

corporation of Delaware Application April 21, 1947, Serial No. 742,857

9 Claims. (01. 250-3351) This invention is directed to directional antennas. More specifically it is directed to direction antennas for use at high radio frequencies.

One method of direction finding by radio, long used at comparatively low radio frequencies, involves the use of the Adcock antenna, an array comprising two vertical receiving antennas so interrelated that the energy generated in the antenna system by a passing wave is proportional to cos where is the angle between the Poynting vector of the Wave and the plane of the antennas. At =90 a null, or no-signal, indication will be found, and it is this null that is used for direction finding. V

In order to rotate such an antenna for direction finding purposes, or to set =90, it is necessary to rotate the entire supporting structure. Inasmuch as an array of this type is unsymmetrical and presents a varying physical aspect to its surroundings, it is undesirable to rotate same at high rates of speed, or even slowly when it is mounted on mobile equipments, such as, for example, on an airplane.

It is an object of this invention, therefore, to provide a mechanically symmetrical directional antenna for very high frequency use, the direc tional pattern of which may be rotated at a high rate of speed with a minimum of mechanical complication.

The above and further objects and novel features will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration only, and are not intended as a definition of the limits of the invention, reference for this purpose being had to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a pictorial view of an antenna in accordance with the instant invention, and

Fig. 2 is a simplified sectional view of the Fig. 1 arrangement, and

Fig. 3 is a sectional view of a portion of the Fig. 2 arrangement, and.

Fig. 4 is an alternative embodiment of this invention.

Referring now to Fig. 1, there is illustrated a pair of colinear right cylinders Ill and II fabricated of conductive material. A ring l2 of insulating material electrically insulates the cylinder H] from the cylinder II. The top of the cylinder I is closed by a metal disc l3 which is insulated from the cylinder by an insulating ring I4. A corresponding insulating ring l5 and a metallic disc i6 is provided at the lower end of the cylinder H. The disc l6 may be a portion of a rigid assembly, not shown, which secures the cylindrical assembly in a fixed relationship with its surroundings.

In Figs. 2 and 3, where Fig. 3 is a section along the line 3-3 of the Fig. 2 View, are shown further constructional details. The cylinder it is partially closed at its lower end by a disc ll having a circular aperture It at its center; correspondingly the cylinder I5 is provided at its top with a similar disc l 9 having an aperture 29. A rotatable hollow metal shaft Zl extends along the axis of the cylindrical assembly, passing through the apertures l3 and 2%. The upper end of the shaft 2i is rotatably secured to and electrically connected to the disc 53 by a bearing 22. At the lower end of the cylindrical structure the shaft 2! passes through an aperture in the center of the disc 16, and is rotatably secured thereto by a second bearing 23. The bearing 23 provides an electrical connection between the disc l 6 and the shaft 2i. Rotating means in the form of a gear wheel 24 is shown whereby the shaft 2i may be mechanically rotated with respect to the cylindrical structure. A substantially cylindrical insulating collar 25 is firmly secured to the shaft 2! in such a position that it is symmetrically disposed above and below the median plane between the discs I? and i9. Annular metal discs 26 and. 21, parallel to and equidistant from the said median plane, are secured to the upper and lower ends, respectively of the collar 25, and are so mounted as to be quite near to, but not touching, the discs H and IS.

A transmission line comprising a grounded outer conductor 28 and a balanced pair of inner conductors 29 and 35! extends upwardly within the shaft 2!. The conductor 29 is connected to the inner edge of the annular disc 25, and the conductor 30 is connected to a point on the same edge of the same disc at a diametrically opposite point. The conductor 29 is also connected to the inner edge of the annular disc Z'l at a point which is in the plane of the two points of connection on the disc 26 and the axis of the cylinders. This latter point of connection of the conductor 29, is, however, on the opposite side of the axis from its point of connection on the disc 25. The conductor 3B is connected to the inner edge of the annular disc 21 at a point diametrically opposite from the point of connection of the conductor 29.

The overall equivalent electrical length of the cylindrical structure is a multiple of M2 where it is the mean operating wavelength, and the diameter of the structure may be of the order of 2.

In operation the radius of the discs 26 and 21 is sufiiciently great with respect to the operating wavelength that the capacitive reactance between the discs 26, 21' and the discs l1 and I9 is rather low. Electric currents on the cylinders it and H therefore are conducted to the transmission line conductors 29 and 30.

A second method of coupling the antenna assembly to the transmission line 28 is illustrated in Fig. 4 wherein a pair of oppositely disposed radial metallic rods 40 and 4| are secured to the insulating collar 25 just above the disc l1, and a second pair of rods 42 and 43 are similarly disposed in proximity to the disc 19. The rods 40, 4|, 42, 43 are in a common plane, and are cross-connected in such a manner that the rod 49 is electrically connected to the rod 43 and to the conductor 36; and the rod 4| is electrically connected to the rod 42 and the conductor 29. The rods are so proportioned and so mounted in relation to the discs l1 and 19 that an equivalent electrical connection is made between the transmission line and diametrically opposed points on the cylindrical surface.

The operation of the Figs. 2 and 4 arrangements are such that when a received wave strikes the cylindrical structure and induces currents thereon, the antenna appears, to the transmission line, to be an Adcock array having its resonant elements in the plane of the rods 4!] to 43, or in the plane of the points of connection to the discs 26 and 21. Thus the cylindrical structure is the electrical equivalent of a symmetrical Adcock array having an infinite number of elements disposed in circular relationship. Rotation of the shaft 28 acts to selectively connect the transmission line 28 to successive Adcock arrays.

What is claimed is:

1. A directional antenna comprising a pair of hollow right cylinders of conductive material juxtaposed in end-to-end coaxial relationship, insulating means joining said cylinders into a structural unit, each of the adjacent ends of said cylinders being partially closed by an annular conductive disc, a hollow shaft extending coaxially through said unit and rotatable with respect thereto, said shaft being insulated from said unit, a pair of identical conductive members carried by but insulated from said shaft, each of said members being located within a respective one of said cylinders and adjacent to but insulated from the aforesaid annular disc forming a part thereof, said conductive members having portions symmetrical with respect to the axis of said unit and lying in a common plane containing said axis, a transmission line enclosed in said shaft and comprising a balanced pair of conductors, each of said conductors being connected to a respective one of the said portions of each of said members, said portions so connected being oppositely disposed with respect to said axis.

2. A directional antenna comprising a pair of hollow right cylinders of conductive material juxtaposed in end-to-end coaxial relationship, insulating means joining said cylinders into a structural unit, each of the adjacent ends of said cylinders being partially closed by an annular conductive disc, a hollow shaft extending coaxially through said unit and rotatable with respect thereto, said shaft being insulated from said unit, a pair of identical conductive members carried by but insulated from said shaft, each of ,4 said members being located within a respective one of said cylinders and adjacent to but insulated from the aforesaid annular disc forming a part thereof, said conductive member being of disc shape, a transmission line enclosed in said shaft and comprising a balanced pair of conductors, each of said conductors being connected to an eccentric point on one of said members and to a corresponding oppositely disposed point on the other of said members.

3. A directional antenna comprising a pair of hollow right cylinders of conductive material juxtaposed in end-to-end coaxial relationship, insulating means joining said cylinders into a structural unit, each of the adjacent ends of said cylinders being partially closed by an annular conductive disc, a hollow shaft extending coaxially through said unit and rotatable with respect thereto, said shaft being insulated from said unit, a pair of identical members carried by but insulated from said shaft, each of said members being located within a respective one of said cylinders and adjacent to but insulated from the aforesaid annular disc forming a part thereof, said members each comprising a pair of conductive rods disposed collinearly along oppositely directed lines radiating from said axis, and insulated from each other, a transmission line enclosed in said shaft and comprising a balanced pair of conductors, each of said conductors being connected to the inner end of a rod of a respective one of said members and to the inner end of the oppositely directed rod of the other of said members.

4. A directional antenna comprising a pair of cylinders of conductive material having a U -shaped cross-sectional configuration, the closed end of each of said cylinders being provided with a central opening, means joining said cylinders into a structural unit in which said cylinders are in coaxial end-to-end relationship with their closed ends adjacent but insulated from each other, a pair of identical conductive members, each of said members being of symmetrical construction with respect to a central point thereof,

means positioning each of said members in adjacent but insulated relationship with respect to a respective one of said closed ends, each of said members being disposed with its central point in coincidence with the axis of said unit and rotatable with the other of said members about said axis, means conductively connecting one point of each of said members with the corresponding oppositely disposed point of the other of said members, and an electrical connection to the electrical mid-point of each of said connecting means.

5. A directional antenna comprising a pair of cylinders of conductive material having a U-shaped cross-sectional configuration, the closed end of each of said cylinders being provided with a central opening, means joining said cylinders into a structural unit in which said cylinders are in coaxial end-to-end relationship with their closed ends adjacent but insulated from each other, a pair of identical conductive members, each of said members being in the shape of an annular disc, means positioning each of said members coaxially of said unit and in adjacent but insulated relationship with respect to a respective one of said closed ends, said members being rotatable together with said axis, means conductively connecting each of two opposite pointson the inner periphery of each of said members to the corresponding oppositely disposed point on the other of said members, and an electrica1 connection to the electrical mid-point of each of said connecting means.

6. A directional antenna comprising a pair of cylinders of conductive material having a U-shaped cross-sectional configuration, the closed end of each of said cylinders being provided with a central opening, means joining said cylinders into a structural unit in which said cylinders are in coaxial end-to-end relationship with their closed ends adjacent but insulated from each other, a pair of identical conductive members, each of said members being of symmetrical construction with respect to a central point thereof, means positioning each of said members in adjacent but insulated relationship with respect to a respective one of said closed ends, each of said members being disposed with its central point in coincidence with the axis of said unit and rotatable with the other of said members about said axis, each of said members comprising a pair of rods insulated from each other and extending collinearly, radially and oppositely with respect to the axis of said unit, means conductively connecting the inner end of each rod of each of said members with the inner end of the oppositely disposed rod of the other of said members, and an electrical connection to the electrical mid-point of each of said connecting means.

7. A directional antenna comprising a pair of vertically extending cup-shaped conductive elements arranged with their closed ends in adjacent but insulated relation, a pair of centrally interrupted conductive devices each symmetrical with respect to the axis of said elements and each disposed in one of said elements in adjacent and parallel relation to the closed end thereof, said devices being mounted for relative rotational movement as a unit with respect to said elements about the axis thereof, means conductively connecting each side of each of said devices to the opposite side of the other and an electrical connection to the electrical mid-point of each of said connecting means.

Number 8. A directional antenna comprising a pair of vertically extending cup-shaped conductive elements arranged with their closed ends in adjacent but insulated relation, the said closed ends being centrally interrupted, a pair of centrally interrupted conductive discs each disposed in a respective one of said elements in coaxial relation thereto and in adjacent parallelism with respect to the closed end thereof, means supporting said discs for relative rotation as a unit with respect to said elements, means conductively connecting each side of each of said discs to the opposite side of the other and an electrical connection to the electrical mid-point of each of said connecting means.

9. A directional antenna comprising a pair of vertically extending cup-shaped conductive elements arranged with their closed ends in adjacent but insulated relation, the said closed ends being centrally interrupted, and a pick-up unit mounted within said elements, said unit comprising in each element a pair of collinear rods insulated from each other and located in adjacent and parallel relation to the closed end of said element, said rods extending symmetrically, radially and oppositely with respect to the axis of said elements, means conductively connecting each rod to the oppositely disposed rod in the other of said elements and an electrical connection to the electrical mid-point of each of said connecting means, said unit being relatively rotatable with respect to said elements.

DAVID W. MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,379,422 Busignies July 3, 1945 2,385,783 Alford Oct. 2, 1945 2,404,196 Seeley July 16, 1946 

